1. Technical Field
The invention relates to an electrical pressure contact comprising a housing sleeve with an end facing the contact and an end facing away from the contact, a conductive contact head that is mounted in the housing sleeve so as to be movable in an axial direction, and which protrudes from the facing the contact end of the housing sleeve, a biasing element that is disposed within the housing sleeve, against whose biasing force the contact head is insertable in the housing sleeve, and a conductive connecting piece that is located at the away from the contact facing end of the housing sleeve for the attachment of an electrical lead.
2. Discussion
Electrical pressure contacts of the initially described kind serve, for example, for current or signal transfer between elements that are movable against one another. The contact head provided in the pressure contact provides, on the one hand, for a resilient mechanical contact with a counter contact that is movable relative to the housing sleeve. On the other hand, an electrical contact to an electrical lead that is fixed to the connecting piece is producible through the conductive contact head.
Electrical pressure contacts of the initially identified type are known from the prior art, which include attached cords on the contact head and the connecting piece. In doing so, the cords are typically twisted, such that they accommodate an insertion of the contact head in the housing sleeve, without kinking. Through this, damaging of the cords can be avoided to a certain degree. Nevertheless, with these pressure contacts, damage frequently arises as a result of a large number of contact stokes, in particular, breaking of the cords. Besides that, the manufacturing of such pressure contacts is comparably complex and expensive.
With respect to the prior art, reference is made to an electrical pressure contact, which is described in EP 1 289 072 A2. This pressure contact has an axially flexible electrical lead, which is clamped with its contact facing end in an axial bore that is formed in the away from the contact facing end of the contact head and is clamped with its away from the contact facing end in an axial bore that is formed in a contact facing end of the connecting piece. Thereby, the flexible electrical lead can be formed of cords or also of a compression spring, against whose spring force the contact head is insertable into the housing sleeve.
DE 39 38 706 C1 discloses an electrical pressure contact, which manages without cords. As shown in FIG. 6, with this pressure contact, the away from the contact facing, i.e., in a housing sleeve 1 inserted portion 2 of a contact head 3 is formed as a hollow cylinder. The wall of the hollow cylinder includes several longitudinal slits 4, whereby wall sectors are formed, which serve as resilient, electrically conductive contact tongues 5. The contact tongues 5 rubbingly lie against the inner surface of the current transferring housing sleeve 1, so that the current can flow over the contact tongues 5 to the housing sleeve 1 and from there to a connection piece 6.
With this pressure contact, contact grease is introduced between the contact tongues 5 and the inner surface of the housing sleeve 1. The contact grease serves to provide for a transfer resistance between the contact tongues 5 and the housing sleeve 1 that is as small as possible and that is constant over time. Thereby, however, the problem appears that, as a result of the contact strokes, the contact grease travels from the interior of the housing sleeve 1 outward, and therefore, the contact grease is no longer available or also, for example, is contaminated by dust particles, which adhere to the contact facing end of the contact head 3 and, with insertion, travels into the interior of the housing sleeve 1. Through this contamination, the contact grease gradually loses both its contact properties as well as its lubrication properties. The loss of the contact properties leads to an increase in the transfer resistance between the contact tongues 5 and the housing sleeve 1, the mechanical properties of the pressure contact degrades through the loss of the greasing properties, so that, for example, the contact head 3 can jam in the spring deflected condition in the housing sleeve 1.
In order to prohibit a deterioration of the contact grease, the end of the contact head 3 projecting out of the housing sleeve 1 is typically cleaned. The typically used cleaning means, however, functions to degrease and make the contact grease likewise gradually ineffective, if the cleaning means travels into the interior of the housing sleeve 1, as a result of the stroke movement of the contact head. In order to replace the now ineffective contact grease with new contact grease, the pressure contact must be dismantled, which is laborious, time intensive and costly. With respect to the prior art, reference is made to EP 0 838 878 A, EP 1 385 233 A, EP 1 102 359, and EP 0 435 408 A.